Sewing machine bobbin



May 23, 1961 G. R. ECKHARDT SEWING MACHINE BOBBIN Filed July 3, 1958 w m H K M! P E G M 4% ATTO R N EYS United States Patent 'I'hepresent invention has to do with sewing machine bobbins andthe'manufacture thereof. It relates particularly to a bobbin which' comprises a central tube and-two parallel sidewalls attached to said'tube. Such bobbins may be made of-metal, plastic or paper.

The present invention contemplatesthe use of paper becauseir is cheap and readily worked to accommodate itself to the method described herein.

The type of bobbin which is herein'describe'd is usually purchasedwith the thread mass 'woundthereon and' after removal of thethreadthe bobbin'itself is discarded; Of necessity such bobbins must be very'lowpriced; This type of bobbin is commonly'used by manufacturers of garments and the like where-it is uneconomical to rewind a--bobbin*because of the time'spent in so doing.

It is desirable with commercial high speed machines to-have' abobbin made of lightweight material so that when the'thread isdrawn ofi'th'e bobbin very rapidly the-bobbin doesnot overrun and cause the thread to tangle in the bobbin case.

It is alsodesirable'to have the sidewalls'of the bobbin stiifenough'so that they do not separate much at the periphery from-'the thread mass and arranged so that the thread-maynot readily jam between-thethread'mass' and theinside of the bobbin walls:

It-isalso desirable to havea bobbin which when wound 40 with thread maintainsits-original dimensions and does not expand-or change-its dimensions as time elapses.

'It-is a lso'desirable to'arrange the bobbinso that'it'will rotate freely within-the bobbincaseotthe sewing machine and so that the peripheral edgesofthe bobbin walls are inthe optimum position in relation to the exit from the bobbin case.

All of these desired resultsand-advantages are obtained with .theipresent invention as will'be more fully described hereinafter.

The following; is a description of my invention, reference being had to the drawings, in which:

Fig. 1 is a-p'er'spective view ofashort'piece of paper tubewith a thread mass wound thereonand a pair of wall blanks fofthe bobbin walls; 7

. Fig. 2' is a longitudinalsectio'n of a pair of dies and a supporting spindle and" the various elements which go to make up the loaded'bobbin;

.Fig. 3 is a sectional viewlike Fig; 2 but taken. after the dies have been brought together to' assemble the various elements of the-bobbing Fig. 4 is aplan view of the finished bobbin;

Fig. 5 is a side viewo'fthe finished bobbin; and

Fig. 6 is a detailed side view of part of the bobbin showing a strand of thread adjacent to a side wall of the bobbin.

Looking at Fig. 1, T shows a thread mass wound on a hollow paper tube 1 in the more or less diagonal direction used in winding such bobbins (a universal wind). It will be noted that the tube 1 on which the thread mass T is wound is somewhat longer than the thickness of the thread mass. This permitsthe wall blanks 2 and 3 to be placed over the ends of the-tube 1 and the'tube and wall blanks locked together, as'will be hereinafter described.

In assembling the walls on the tube, shaping the same and compressing the thread mass, a pair ofd-ies, such' as' those shown in Figs. 2 and 3, are used. The upper die member is shown at 5, the lower die member at 6. The faces of dies 5 and 6 are furnished with radially disposed corrugations, those on die 5 are'shown at 7 and those on die 6 at 8.

lock the walls of the bobbin and the tube together. The bushing for die member 5 is shown at 9 and the bushing for die member 6 at 10. A central spindle 11 is designed to pass freely but snugly through the central-bore of the bobbin blank and the bushings 9 and 10:0f the dies; This spindle serves to center the blank and'prevents collapse of the tube 1 during the compression of'the bobbin blank and thread mass.

In the operation of the die mechanism, the1bobbin= elements shown in Fig. 1, that is, the tube' 1 withthe'thread mass T thereon, and the tubewall blanks 2 and: 3' are assembled on the spindlell as shown in Fig; 2. The dies.

are then'movedtoward each'other to the position shown in Fig. 3. During this operation the tube 1' is. compressedlongitudinally to'a small extent as shown in Fig. 3 and the ends of the tube are turned over'and' locked into engagement with'th'e outside. surfaces of the walls'of the lt is desirable that these corrugations bereasonably" deep and pronounced. However, there is a limitto thepressure which may be imposed on the thread without injuring it and it is desirable that theraised-surfacesorr one wall are disposed opposite to the depressed surfaces on the opposite wall so that the thickness-of the threadmass remainsconstant. away from a central plane disposed between and parallel to the side walls of the bobbin. Depressed means/the- A portion.

opposite, i.e., toward such a central plane. of a surface is considered raised with respect. to another depressed portion when it lies farther fromsuch.

a central plane than the latter portion. The corrugations.

may take someother shapeordisposition th an.-radial,-. 0 butit is desirable that they exist. on both sides: of each.

wall, as shown in'the figure. This result can. bereadily.

obtained-with relatively thin paper bobbin sidewalls. As.

shown in Fig. 6 the edge view ofthe corrugated. wall3 may be of a wavelike or undulating form. when developed.- 5 This smooth curve allows proper pressure on the thread. mass with less danger of cutting or straining the thread.- than might be the case if sharper corrugations were imrpressed.

moved from the dies.

It. is desirable to heat the die members because they will more readily shape the elements of the bobbin and the thread mass and the finished article will hold its dimensions and shape better if compressed under heat. The dies may be heated by electric resistance elements or by circulating heated liquid therethrough. These features are not shown because their structure is no part of this invention. A temperature of about 250 F. hasbeen found advantageous with a paper bobbin and any conventional sewing thread wound on it.

A bobbin made in accordance with the method herein Patented May 23, 1961.

Each die is also furnished with acentral bushing, the surface of which is specifically designed to Raised as used herein means disclosed has a number of advantages. It is economical because it may be made of paper. It is so constructed that it is relatively strong with the walls firmly locked to the tube. It carries maximum length of thread because the thread mass is compressed. It is economical to make because the assembly of the bobbin, compression of the thread mass and the formation of the corrugations on the walls of the bobbin are all performed in one operation.

The corrugated side walls of the bobbin are advantageous for a number of reasons. They, of course, strengthen and stiffen the walls so as to minimize the spreading apart of the walls and the separation of the walls from the thread mass. In conjunction with the projecting ends of the tube they permit ready rotation of the bobbin in the bobbin case without sticking. The free and smooth unwinding of the thread is an important feature in high speed machines. Because the raised areas on one wall are opposite to the depressed areas on the opposite wall, the thread mass is evenly compressed and there are no high and low points of compression in the thread mass especially around the periphery thereof which is the case if the raised points of one wall are opposite to the raised points of the other wall. This permits of a higher average compression without injury to the thread.

It is also true when the respective corrugations are arranged, as shown in Fig. 5, that there is less tendency for the thread mass and walls to separate so that there is less chance in case of a backlash of the thread finding its way down between the thread mass and the walls to jam and cause breakage. This feature is illustrated in Fig. 6 where a strand of thread 20 is shown overlying the protuberances 22 with the thread mass at T and one of the side walls of the bobbin at 3. It will be seen that if the thread finds its way over to the side wall 3, with a tendency to go down between the thread mass T and the wall 3 into gap 21, it is prevented from doing so by protuberances 22 on the thread mass which follow closely the corrugations in the wall '3. This improved result follows from the fact that the raised point on one Wall is opposite the depressed point on the other and the thickness of the thread mass is constant. When the corrugations in the respective walls are arranged otherwise, the thread mass is apt to be more highly compressed between the depressed corrugations and less compressed between the raised corrugations and, of course, the high pressure will tend to cause the depressed portions of the thread mass to snap back more than the raised portions, thus reducing the depth of the corrugations It is probably also true that when the thread mass is compressed in a corrugated bobbin of the kind disclosed and when the thread mass is wound in the conventional diagonal manner shown in Figs. 1 and there is an internal shifting of the various layers in-the thread mass, one in relation to the other, which brings about a frictional resistance to a return to the original condition of the thread mass which in turn means that the thread mass is more inclined to retain the shape and form impressed upon it by dies of the character shown in Figs. 2 and 3. If the corrugations on the two walls were disposed other than as shown herein, that is, if the depressed portions in the two walls were opposite to each other and the raised portions opposite to each other, this internal shifting and creating of friction between the layers is not present, at least not to a marked extent, and there is a greater tendency for the thread mass to expand and attempt to go back to the condition it was in before being compressed by the dies.

The deeper corrugations and the relation of those on one wall to the other bring about a more desirable bobbin which is stiffer, less apt to tangle and which rotates freely and easily within the bobbin case.

Although but a specific embodiment of the invention is herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of the invention as defined by the following claims.

What is claimed is:

1. In a sewing machine bobbin having a central tube connecting two annular side walls and wound with a thread mass having side surfaces opposed to said side walls, an improvement comprising raised and depressed areas of the side walls, each raised area of one side wall lying opposite a depressed area of the other side wall and the side surfaces of the thread mass conformed to the raised and depressed areas of the side walls.

2. A wound sewing machine bobbin as described in claim 1 in which a protrusion on the side surface of the compressed thread mass enters far enough into each raised area of the side walls so that a thread stretched between the two adjacent depressed areas of the same side wall overlies the protrusion;

3. In a sewing machine bobbin having a central tube connecting two annular side walls and wound with a thread mass having side surfaces opposed to said side walls, an improvement comprising corrugations in the side surfacesso proportioned and distributed that the distance through the thread mass from one side surface to the other, measured in a direction parallel to the axis of central tube, is the same for all points on the side surfaces whichare equidistant from the axis of the central tube and corrugations in the side walls conformed to those in the side surfaces. r

4. In a sewing machine bobbin having a central tube of paper connecting two annular paper side walls and wound with a thread mass having side surfaces opposed to said side walls, an improvement comprising radially extending raised and depresed areas of the side walls, the'raised area of one side wall lying opposite a depressed area of the other side wall, the side surfaces of the thread mass conformed to the raised and depressed areas of the side walls, and in which a protrusion on the side surface of the thread mass enters far enough into each raised area of the side walls so that a thread stretched betweenthe two adjacent depressed areas of the same side wall overlies the protrusion. Y

5. The sewing machine bobbin of claim 4 in which the developed edges of the side walls have wavelike form.

References Cited in the file of this patent UNITED STATES PATENTS 

